1. Field of the Invention
The present invention relates to a liquid crystal panel and a liquid crystal display that display image with liquid crystals.
2. Description of the Background Art
In general, a liquid crystal display includes an array substrate and a counter substrate bonded to each other through a sealing material. The array substrate is the substrate that includes, for example, a thin film transistor (TFT). The counter substrate is the substrate facing the array substrate. The space defined by, for example, the array substrate, the counter substrate, and the sealing material is filed with liquid crystals. In the periphery of the array substrate, the common wiring for supplying voltage for use in the driving of the liquid crystal display is located.
The liquid crystal displays in recent times are required to have a wide viewing angle. Thus, the liquid crystal displays commonly include liquid crystal panels employing the fringe field switching (FFS) mode. In the liquid crystal panel employing the FFS mode, both the pixel electrode and the common electrode that control the alignment of liquid crystals are located on the array substrate. The pixel electrode and the common electrode are stacked with the insulating film located therebetween. The pixel electrode or the common electrode, being one of the two electrodes that is located on the upper layer side, has slits. One of the surfaces of the array substrate that is in contact with liquid crystals is rubbed in the direction substantially parallel to the longitudinal direction of the slits.
In a case where the potential between the two electrodes mentioned above is the OFF potential, liquid crystal molecules forming liquid crystals are aligned in the direction substantially parallel to the longitudinal direction of the slits. Upon application of a potential greater than the OFF potential between the two electrodes, an electric field (a transverse electric field) is generated in the direction vertical to the long sides of the slits. In this case, the liquid crystal molecules rotate (laterally) in a plane parallel to the substrate along the electric field.
In such liquid crystal display, the angle of rotation of the liquid crystal molecules is controlled, whereby the amount of light transmission is controlled. Besides the FFS mode, the in-plane switching (IPS) mode is widely known as the mode of the liquid crystal panel having the structure including both the pixel electrode and the common electrode located on the array substrate.
The liquid crystal displays employing, for example, the FFS mode and the IPS mode are likely to have display defects caused by the electrically charged surface of the liquid crystal panels. Japanese Patent Application Laid-Open No. 09-105918 (1997) (FIG. 14) discloses the technique (hereinafter also referred to as “related art A”) of preventing the occurrence of defective displaying resulting from electrification due to, for example, static electricity. In particular, according to the related art A, a conductive layer is formed on one of the surfaces of the upper substrate (counter substrate) that is not in contact with liquid crystals. The conductive layer is grounded. In other words, the conductive layer is connected to the earth terminal that is kept at the ground potential.
In recent years, there has been a growing demand for smaller and lighter display panels including narrower frames mainly as liquid crystal panels and organic electroluminescent (EL) panels. The display panels, such as the liquid crystal panels and the organic electroluminescent panels, including the touch functionality of receiving operations by users are becoming increasingly popular. With this trend, the display panels are more likely to malfunction due to electric discharge caused by static electricity accumulated in, for example, the human body.
As an example, the following describes the liquid crystal panel. In general, the common wiring is located in the periphery of the array substrate included in the liquid crystal panel. In many cases, the edge portion of the common wiring extends off the sealing material in plan view. Thus, electric charges reaching the periphery of the liquid crystal panel (array substrate) due to electric discharge caused by static electricity are more likely to be transmitted to the driver integrated circuit (IC) through the common wiring in the array substrate. The driver IC is, for example, a chip-on-glass (COG) mounted IC or a chip-on-film (COF) mounted IC on the circuit board electrically connected to the array substrate. The above-mentioned situation raises the possibility of, for example, a malfunction or a failure of the driver IC.
Japanese Patent Application Laid-Open No. 2008-046278 discloses the technique (hereinafter also referred to as “related art B”) of preventing the liquid crystal panels (liquid crystal displays) from malfunctioning due to electric discharge. In particular, according to the related art B, the common wiring is located inward from the seal in plan view. The wiring (ground wiring) connected to the ground potential is located so as to surround the common wiring. The above-mentioned wiring is connected to the protruding portions located outside of the seal in plan view. The protruding portions are connected to the ground potential.
The malfunctions caused by static electricity can be eliminated or reduced to a greater extent by the related art B than by the related art A. Unfortunately, according to the related art B, one piece of wiring (ground wiring) surrounds the common wiring and is connected to the ground potential. Thus, according to the related art B, charges associated with electric discharge due to static electricity are more likely to be transmitted to the common wiring through the ground wiring. The common wiring is used to drive the liquid crystal panel (liquid crystal display). For example, various malfunctions would occur in the liquid crystal panel (liquid crystal display) if charges associated with electric discharge are transmitted to the common wiring. Such malfunctions include a failure of the liquid crystal panel. Thus, the related art B would raise the considerable possibility of malfunctions associated with electric discharge due to static electricity. To eliminate or reduce the occurrence of malfunctions associated with electric discharge, the transmittance of charges associated with electric discharge to the common wiring need to be eliminated or reduced.